<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8" />
    <title>Document</title>
    <script src='lib/webgl-utils.js'></script>
    <script src='lib/webgl-debug.js'></script>
    <script src='lib/cuon-utils.js'></script>
    <script src="lib/cuon-matrix.js"></script>

</head>
<body onload="main()">
<canvas id="mybox" width="500" height="500">
    请更换新版浏览器查看效果!
</canvas>

<script >
    let VSHADER_SOURCE=`
    attribute vec4 a_position;
    attribute float a_pointSize;
    void main(){
        gl_Position=a_position;
        gl_PointSize=a_pointSize;
        }`;
    let FSHADER_SOURCE=`
    void main(){
        gl_FragColor=vec4(1.0,0.3,0.3,1.0);
        }`;

    function main(){
        let canvas=document.getElementById('mybox')
        let gl=getWebGLContext(canvas)
        if(!initShaders(gl,VSHADER_SOURCE,FSHADER_SOURCE)){
            console.log('初始化shader失败');
            return;
        }
        let n=initVertexBuffers(gl)
        if(n<0){
            console.log('设置顶点位置失败')
            return;
        }
        gl.clearColor(0.0,0.0,0.0,1.0)
        gl.clear(gl.COLOR_BUFFER_BIT)
        gl.drawArrays(gl.POINT,0,n);

    }

    function initVertexBuffers(gl){
        let vertices=new Float32Array([0.0,0.3,-0.3,0.0,0.3,0.0])
        let n=3;
        let sizes=new Float32Array([10.0,13.0,15.0]);
        let vertexBuffer=gl.createBuffer();
        let sizeBuffer=gl.createBuffer();

        gl.bindBuffer(gl.ARRAY_BUFFER,vertexBuffer);
        gl.bufferData(gl.ARRAY_BUFFER,vertices,gl.STATIC_DRAW);
        let a_position=gl.getAttribLocation(gl.program,'a_position');
        gl.vertexAttribPointer(a_position,2,gl.FLOAT,false,0,0)
        gl.enableVertexAttribArray(a_position);

        gl.bindBuffer(gl.ARRAY_BUFFER,sizeBuffer)
        gl.bufferData(gl.ARRAY_BUFFER,sizes,gl.STATIC_DRAW);
        let a_pointSize=gl.getAttribLocation(gl.program,'a_pointSize');
        gl.vertexAttribPointer(a_pointSize,1,gl.FLOAT,false,0,0)
        gl.enableVertexAttribArray(a_pointSize)
        
        return n;
    }
   


</script>

</body>
</html>